Centering and smoothing apparatus



March 26, 1963 e. KEHR ETAL CENTERING AND SMOOTHING APPARATUS Filed Dec. 9, 1960 llll Ail/I' m errfor' na United States CENTERING AND SMOOTHING APPARATUS Giinther Kelir, Klaus-Groth Strasse 59, Bremen, Germany, and Christian Heinrich Wichmann, Brannschweiger Strasse 76, Thedinghansen, Germany Fiicd Dec. 9, 1960, Ser. No. 74,858 Claims priority, application Germany Feb. 11, 1960 7 Claims. (Cl. 77-18) The present invention relates to a centering and smoothing apparatus for center bores of hardened shafts, pinions, bolts, or similar workpieces.

The center bores of workpieces are smoothed in the usual manner by grinding first one and then the other center bore of each workpiece by means of grinding wheels. In this operation, the workpiece is held stationary, while the grinding wheel is driven.

This known method of smoothing center bores has a series of disadvantages, among them being the fact that the known manner of grinding requires a considerable length of time since it has to be carried out twice successively on each workpiece. Funthermore, the grinding wheel wears off very quickly and therefore has to be frequently replaced, and even after grinding only for a short time, the grinding wheel becomes smudged and smeary by the material which has been ground oft", and it will then no longer work with the required accuracy. It must therefore be dressed repeatedly which, in turn, easily results in inaccurate surfaces. Further inaccuracies easily occur when the workpiece is being clamped for this grinding operation with the result that the two center bores when finished may not exactly coincide with the true center of the workpiece. Finally, there is the disadvant-age that, due to the grinding, the surfaces of the center bores become rough and that the center points will therefore wear 01f quickly when one workpiece is ground after another, so that the grinding operation can soon no longer be carried out at the required accuracy.

It is an object of the present invention to provide an apparatus for centering and smoothing center bores of hardened shafts, pinions, bolts, or similar workpieces, which is adapted to carry out the smoothing and centering operations on the center bores simultaneously and to avoid the disadvantages of the known smooothing method.

An inventive feature of this apparatus consists in the provision of two opposite stationary hard-metal center points which are provided with five cutting edges and are mounted in accurate axial alignment with each other and are used for clamping the workpiece by the insertion of these points into the center bores, and in the provision of means for driving the workpiece.

According to one preferred embodiment of the invention, one of the two cutting center points is adjustable in the axial direction under the action of a spring and is pressed by this spring against the workpiece so that the latter is clamped resiliently between the two points.

The apparatus according to the invention has the advantage that both center bores of a workpiece may be worked upon simultaneously and in accurate alignment with the center of the workpiece so that considerable time will be saved as compared with the length of time which was required by the previous smoothing method. If the workpiece is slightly out of true, as it may result from the hardening operation, this will also be automatically compensated without requiring the workpiece to be straightened. The two center bores are then finished with great accuracy since they are lapped by means of the hard-metal cutting points. The center bores when being smoothed are also given the accurate particular angul-arity which is required for the subsequent grinding operation on the workpiece.

3,8Z,h i Patented Mar. 26, 1963 ice If the apparatus is mounted next to a grinding machine, it will not require a separate operator, but both machines may be manipulated by the same operator.

A further feature of the invention consists in providing the new apparatus with a device for retracting the axially movable hard-metal cutting point from the workpiece against the action of the spring, for example, by means of a cable which is operated by a foot lever. It is in this connection also advisable to provide between the hardmetal cutting points one or more prismatic bearing elements which are adapted to receive the workpiece before the same is being clamped between the center points and which may be adjusted in the vertical direction.

The above-mentioned features permit the apparatus to be Very easily and quickly manipulated. After operating the foot lever the operator only needs to lay the workpiece upon the prismatic bearings between the two cutting center points. After releasing the foot lever, the workpiece will be automatically clamped between the center points whereby the workpiece will be lifted slightly olf the prismatic bearings so that no more needs to be done than to start the drive mechanism. The required operation on the workpiece is then carried out automatically since the apparatus according to the invention is provided with an adjustable time relay which limits the length of time of each operation.

According to another preferred feature of the invention, each of the cutting center points is provided with a central drill which is movable in the axial direction under the action of a spring and is nonrotatable relative to the points. This central drill permits the coating and other residues from the hardening operation at the bottom of the center bores to be automatically removed While the bores themselves are being smoothed. Prior to this invention it was necessary to scrape out these residues from the inner ends of the center bores by means of a wire or other suitable instrument and then to blow them out of the bores by means of compressed The above-mentioned as well as additional objects, features and advantages of the present invention will become more apparent from the following detailed description of one particular embodiment thereof which is illustrated in the accompanying drawings, in which- FIGURE 1 shows, partly in section a side view of the apparatus;

FIGURE 2 shows a cross section taken along line IIII of FIGURE 1;

FIGURE. 3 shows a longitudinal section of the drive elements;

FIGURE 4 shows a longitudinal section of the tailstock;

FIGURE 5 shows a side view of a hard-metal cutting point;

FIGURE 6 shows a front view of the center point according to FIGURE 5; while FIGURE 7 shows a longitudinal section of a hard-metal cutting point which is provided with a central drill.

Referring to the drawings, the apparatus according to the invention comprises a pair of opposite, substantially stationary hard-metal center points 10 and 21 which are preferably provided with live cutting edges and are mounted in accurate axial alignment with each other. They are used for mounting a workpiece 11 by engaging into the center bores 12 thereof.

The workpiece may be driven by a drive mechanism, generally indicated at 13 which consists of stepped V-belt pulleys 14 and 15 which are driven by an electric motor 16, and of a driving disk 17 which is provided with at least one carrier bolt 18 on which a work-driving member 19 engages which is clamped upon the workpiece 1'1. Pulley 15 together with driving disk 17 are rotatably mounted on a stationary shaft 20 which also serves as the support of the cutting center point It).

The other cutting center point 21 is slidable in the axial direction under the action of a spring 22 which presses center point 21 against workpiece 11 which is thus resiliently clamped between the two points 29 and 21. For this purpose, center point 21 is inserted into a shaft 26 which is slidable within a tailstock barrel 27, in which it is secured against rotation by a bolt 25 which engages into a groove 24 in shaft 26. This shaft 26 is acted upon by spring '22, and together with center point 21 it is adapted to be retracted from the workpiece against the action of spring 22 by means of a cable 28 which extends through the hollow adjusting screw 23 and is connected to an eye 29 on the rear end of shaft 26. Cable 23 is guided by a pulley St} to lead in the downward direction to a foot lever, not shown, by means of which the cable may be retracted to retract center point 21 from the workpiece. The tension of spring 22 is adjustable, for example, by means of the adjusting screw 23.

Between the hard-metal cutting center points It and 2 1, one or more prismatic bearing members 31 are provided for receiving and holding the workpiece 11 before being clamped between points if and 21. These bearing members 31 are vertically adjustable to elevate the workpiece to a level at which center points 1% and 21 can engage into the center bores 12 and thereby slightly lift the workpiece so that it will be able to rotate freely above the prismatic bearing members 31. These bearing members 31 as well as tailstock 27 are slidable along guide bars 32 or the like on which they may be adjusted and secured in a fixed position.

FIGURES and 6 illustrate a hard-metal cutting center point or 21 which is provided with five cutting or scraping edges.

FIGURE 7 shows a modification of one of the hardmetal cutting points itia or 21a according to the invention in which the body of the center point is provided with a central longitudinal bore in which a central drill 34- is mounted so as to be slidable against the action of a spring 33. Drill 34 is prevented from rotating relative to the center point 10a or 21a by a pin 36 which engages in a longitudinal groove 35 in the head of drill 34. This central drill is adapted to enter into the bottom 12a of the respective center bore 12 of workpiece 11 to scrape and clean out any residues from the hardening operation.

For cooling the tools and the workpiece and for washing away the particles which have been removed from the center bore by the smoothing operation, a suitable coolant is conducted to the center points in the conventional manner through tubes 37 and 38.

Although our invention has been illustrated and described with reference to the preferred embodiments thereof, we wish to have it understood that it is in no way limited to the details of such embodiment, but is capable of numerous modifications Within the scope of the appended claims.

Having thus fully disclosed our invention, what we claim is:

1. In an apparatus for centering and smoothing a pair of coaxial center bores of a workpiece, in combination, a pair of coaxial shaft means for respectively carrying a pair of coaxial tools for centering and smoothing the center bores of a workpiece; a pair of support means respectively carrying said pair of shaft means and prevent ing rotation thereof, one of said support means supporting the shaft means carried thereby for axial movement toward and away from the other of said shaft means; and drive means for rotating a workpiece mounted on the tools carried by said pair of shaft means so that the center bores of the workpiece will be centered and smoothed by said tools.

2. In an apparatus for centering and smoothing a pair of coaxial center bores of a workpiece, in combination, a pair of coaxial shaft means for respectively carrying a pair of coaxial tools for centering and smoothing the center bores of a workpiece; a pair of support means respectively carrying said pair of shaft means and preventing rotation thereof, one of said support means supporting the shaft means carried thereby for axial movement toward and away from the other of said shaft means; drive means for rotating a workpiece mounted on the tools carried by said pair of shaft means so that the center bores of the workpiece will be centered and smoothed by said tools; and spring means urging the shaft means carried by said one support means toward the other shaft means.

3. In an apparatus for centering and smoothing a pair of coaxial center bores of a workpiece, in combination, a pair of coaxial shaft means for respectively carrying a pair of coaxial tools for centering and smoothing the center bores of a workpiece; a pair of support means respectively carrying said pair of shaft means and preventing rotation thereof, one of said support means supporting the shaft means carried thereby for axial movement toward and away from the other of said shaft means; drive means for rotating a workpiece mounted on the tools carried by said pair of shaft means so that the center bores f the workpiece will be centered and smoothed by said tools; spring means urging the shaft means carried by said one support means toward the other shaft means; and a cable connected to said shaft means carried by said one support means for moving said latter shaft means in opposition to said spring means away from the other shaft means so that a workpiece may be placed between the tools and thereafter the cable may be released so as to release the shaft means carried by said one support means to said spring means whereby the latter shaft means will move toward the other shaft means so that the pair of tools will engage the workpiece in the center bores thereof.

4. In an apparatus for centering and smoothing a pair of coaxial center bores of a workpiece, in combination, a pair of coaxial shaft means for respectively carrying a pair of coaxial tools for centering and smoothing the center bores of a workpiece; a pair of support means respectively carrying said pair of shaft means and preventing rotation thereof, one of said support means supporting the shaft means carried thereby for axial move-: ment toward and away from the other of said shaft means; and drive means for rotating a workpiece mounted on the tools carried by said pair of shaft means so that the center bores of the workpiece will be centered and smoothed by said tools, said drive means including a rotary drive member supported for rotary movement by one of said shaft means.

5. In an apparatus for centering and smoothing a pair of coaxial center bores of a workpiece, in combination, a pair of coaxial shaft means for respectively carrying a pair of coaxial tools for centering and smoothing the center bores of a workpiece; a pair of support means respectively carrying said pair of shaft means and preventing rotation thereof, one of said support means supporting the shaft means carried thereby for axial movement toward and away from the other of said shaft means; drive means for rotating a workpiece mounted on the tools carried by said pair of shaft means so that the center bores of the workpiece will be centered and smoothed by said tools; and third support means located adjacent the space between said pair of shaft means for supporting a workpiece with its axis almost at the elevation of the common axis of said pair of shaft means so that when the tools enter into the center bores of the workpiece the workpiece will be raised from said third support means through a slight distance so as to be freely rotatable without engaging the third support means.

6. In a machine for centering and smoothing center bores of workpieces, in combination, a pair of coaxial shaft means; support means carrying said pair of shaft means and preventing the same from rotating, one of said aosae support means supporting one of said shaft means for movement axially toward and away from the other of said shaft means; a pair of centering and smoothing tools respectively carried by said pair of shaft means and respectively having working ends directed toward each other, said tools also being coaxial and each Working end having the configuration of a pyramid having a plu rality of fiat sides intersecting at straight edges which form the cutting edges of the working end of each tool; and drive means for rotating a workpiece carried by said tools with respect to the latter so that said straight cutting edges wiil smooth. and center the center bores or" a workpiece.

7. In a machine for centering and smoothing center horse of workpieces, in combination, a pair of coaxial shaft means; support means carrying said pair of shaft means and preventing the same from rotating, one of said support means supporting one of said shaft means for movement axially toward and away from the other of said shafit means; a pair of centering and smoothing tools respectively carried by said pair of shaft means and respectively having working ends directed toward each other, said tools also being coaxial and each working end having the configuration of a pyramid having a plurality of fiat sides intersecting at straight edges which form the cutting edges of the working end of each tool; and drive means for rotating a Work :iece carried by said tools with respect to the otter so that said straight cutting edges will smooth and center the center bores of a workpiece, at least one of said tools being formed with an axial bore passing through said Working end thereof and said one tool carrying a springpressed drill means which projects through said bore of said working end thereof beyond said woriing end so as to engage the innermost part of one of the center bores of the workpiece.

References Qited in the file of this patent UNITED STATES PATENTS 

1. IN AN APPARATUS FOR CENTERING AND SMOOTHING A PAIR OF COAXIAL CENTER BORES OF A WORKPIECE, IN COMBINATION, A PAIR OF COAXIAL SHAFT MEANS FOR RESPECTIVELY CARRYING A PAIR OF COAXIAL TOOLS FOR CENTERING AND SMOOTHING THE CENTER BORES OF A WORKPIECE; A PAIR OF SUPPORT MEANS RESPECTIVELY CARRYING SAID PAIR OF SHAFT MEANS AND PREVENTING ROTATION THEREOF, ONE OF SAID SUPPORT MEANS SUPPORTING THE SHAFT MEANS CARRIED THEREBY FOR AXIAL MOVEMENT TOWARD AND AWAY FROM THE OTHER OF SAID SHAFT MEANS; AND DRIVE MEANS FOR ROTATING A WORKPIECE MOUNTED ON 